The use of cement paste for sealing cracks in concrete and in masonry has proved to be suitable for more than 100 years. The broad distribution of the grain sizes of normal cement usually used in cement glue and the dehydration of usual suspensions made of such normal cement, however, limit their application for restoration and repair of concrete masonry. Furthermore, suspensions of normal cement are unsuitable for the stabilisation of grounds with fine grain size. While the high amount of coarse cement grains makes the intrusion of the cement paste into fine cracks and gaps difficult or even impossible, the setting reactions decisive for the strength are disturbed or hindered by the dehydration. The repair of buildings, be it buildings of historic significance, be it buildings constructed some decades ago or only recently, falls within the most important and at the same time most fastidious problems of an injection specialist. In order to enable an improved intrusion into the finest cracks and into cavities being situated deep below the surface, products applicable by injection have been developed. Such injections can either be performed from the surface or by perforated injection hoses already run in the building. In order to get a successful injection, long lasting stable compositions of micro cement with suitable additives are necessary, since only such compositions guarantee the desired consistency of the suspension in the liquid phase. Upon setting, such injection cements are able to form strong connections of the same rigidity as concrete and mortar. Micro cements have a density of about 3.10 g/cm.sup.3 and a Blaine value of 8.000 g/cm.sup.2 to 20.000 g/cm.sup.2.
Typical grain size distributions of a micro cement are:
______________________________________ smaller than 2 .mu.m about 25% smaller than 4 .mu.m about 32% smaller than 8 .mu.m about 20% smaller than 16 .mu.m about 23% ______________________________________
Typical development of the compressive strength:
______________________________________ after 1 day: about 40 N/mm.sup.2 after 2 days: about 50 N/mm.sup.2 after 7 days: about 60 N/mm.sup.2 after 28 days: about 65 N/mm.sup.2 ______________________________________
Although such injection cements represent a significant progress in comparison with normal cement paste, their application does not enable a sufficient corrosion protection. Of course water penetration to the reinforcements is markedly reduced, however, humidity remaining in the building as well as corrosion promoting substances can still have a detrimental effect on the reinforcements.
EP 0 247 773 discloses the introduction of corrosion inhibitors, for example on a support material in bore holes especially made for said purpose. Said procedure has the disadvantage that on the one hand a mechanical treatment of the building to be restored becomes necessary, on the other hand the corrosion inhibitor is not directly added to the most endangered places due to crack formation.
It is also already known from EP 0 635 463 A1 to add corrosion inhibitors to normal cement used in building construction in order to avoid corrosion of metal reinforcements. However, such cements are not suitable for the repair of buildings due to the above mentioned disadvantages of compositions comprising normal cement which markedly limits their applicability to fill cracks and cavities.
In NL 6 906 625 a covering material is described that comprises a large amount of zinc powder admixed with a binder such as e.g. fine granulated cement. However, such a composition, due to the large amount of zinc and zinc components, is unsuitable for the repair of buildings and furthermore, zinc is an unsuitable corrosion inhibitor for reinforcing irons due to its highly limited migration ability.